OVO

But are there ultimate explanations? The doctrine which I have called ‘essentialism’ amounts to the view that science must seek ultimate explanations in terms of essences: if we can explain the behaviour of a thing in terms of its essence – of its essential properties – then no further question can be raised, and none need be raised (except perhaps the theological question of the Creator of the essences). Thus Descartes believed that he had explained physics in terms of the essence of a physical body which, he taught, was extension; and some Newtonians, following Roger Cotes, believed that the essence of matter was its inertia and its power to attract other matter, and that Newton’s theory could be derived from, and thus ultimately explained by, these essential properties of all matter. Newton himself was of a different opinion. It was a hypothesis concerning the ultimate or essentialist causal explanation of gravity itself which he had in mind when he wrote in the Scholium generale at the end of the Principia: ‘So far I have explained the phenomena… by the force of gravity, but I have not yet ascertained the cause of gravity itself… and I do not arbitrarily [or ad hoc] invent hypotheses.’

I do not believe in the essentialist doctrine of ultimate explanation. In the past, critics of this doctrine have been, as a rule, instrumentalists: they interpreted scientific theories as nothing but instruments for prediction, without any explanatory power. I do not agree with them either. But there is a third possibility, a ‘third view’, as I have called it. It has been well described as a ‘modified essentialism’ – with emphasis upon the word ‘modified’.

This ‘third view’ which I uphold modifies essentialism in a radical manner. First of all, I reject the idea of an ultimate explanation: I maintain that every explanation may be further explained, by a theory or conjecture of a higher degree of universality. There can be no explanation which is not in need of a further explanation, for none can be a self-explanatory description of an essence (such as an essentialist definition of body, as suggested by Descartes). Secondly, I reject all what-is questions: questions asking what a thing is, what is its essence, or its true nature. For we must give up the view, characteristic of essentialism, that in every single thing there is an essence, an inherent nature or principle (such as the spirit of wine in wine), which necessarily causes it to be what it is, and thus to act as it does. This animistic view explains nothing; but it has led essentialists (like Newton) to shun relational properties, such as gravity, and to believe, on grounds felt to be a priori valid, that a satisfactory explanation must be in terms of inherent properties (as opposed to relational properties). The third and last modification of essentialism is this. We must give up the view, closely connected with animism (and characteristic of Aristotle as opposed to Plato), that it is the essential properties inherent in each individual or singular thing which may be appealed to as the explanation of this thing’s behaviour. For this view completely fails to throw any light whatever on the question why different individual things should behave in like manner. If it is said, ‘because their essences are alike’, the new question arises: why should there not be as many different essences as there are different things?

Plato tried to solve precisely this problem by saying that like individual things are the offspring, and thus copies, of the same original ‘Form’, which is therefore something ‘outside’ and ‘prior’ and ‘superior’ to the various individual things; and indeed, we have as yet no better theory of likeness. Even today, we appeal to their common origin if we wish to explain the likeness of two men, or of a bird and a fish, or of two beds, or two motor cars, or two languages, or two legal procedures; that is to say, we explain similarity in the main genetically; and if we make a metaphysical system out of this, it is liable to become a historicist philosophy. Plato’s solution was rejected by Aristotle; but since Aristotle’s version of essentialism does not contain even a hint of a solution, it seems that he never quite grasped the problem.

By choosing explanations in terms of universal laws of nature, we offer a solution to precisely this last (Platonic) problem. For we conceive all individual things, and all singular facts, to be subject to these laws. The laws (which in their turn are in need of further explanation) thus explain regularities or similarities of individual things or singular facts or events. And these laws are not inherent in the singular things. (Nor are they Platonic ideas outside the world.) Laws of nature are conceived, rather, as (conjectural) descriptions of the structural properties of nature – of our world itself.

Here then is the similarity between my own view (the ‘third view’) and essentialism; although I do not think that we can ever describe, by our universal laws, an ultimate essence of the world, I do not doubt that we may seek to probe deeper and deeper into the structure of our world or, as we might say, into properties of the world that are more and more essential, or of greater and greater depth.

Every time we proceed to explain some conjectural law or theory by a new conjectural theory of a higher degree of universality, we are discovering more about the world, trying to penetrate deeper into its secrets. And every time we succeed in falsifying a theory of this kind, we make a new important discovery. For these falsifications are most important. They teach us the unexpected; and they reassure us that, although our theories are made by ourselves, although they are our own inventions, they are none the less genuine assertions about the world; for they can clash with something we never made.

From Ratio, December 1957.  Reprinted in Objective Knowledge.  Oxford: Clarendon Press, 1986